To deal with the bio-refractory substances of penicillin in antibiotic wastewater, boron-doped diamond (BDD) electrodes prepared by direct current plasma chemical vapor deposition system were used to investigate the degradation rule and pathway of penicillin wastewater with penicillin G sodium as target pollutant. Results show that penicillin G sodium with different concentrations could be completely degraded at BDD electrodes by electrochemical combustion reaction. The degradation of penicillin G sodium and chemical oxygen demand (COD) accorded with the pseudo-first-order rate kinetics. When the current density was increased from 10 mA/cm² to 20 mA/cm², the apparent reaction rate constant of penicillin G sodium and COD increased by 51.3% and 29.1%, respectively. The degradation of penicillin G sodium at BDD electrodes was controlled by mass transfer in liquid phase. The concentration of penicillin G sodium and current density greatly influenced the current efficient (E_C). Major intermediate products of the degradation pathway of penicillin G sodium at BDD electrodes were penillic acid, isopenillic acid, penicillenic acid, and penicilloic acid.